<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<button id="btn1">嘻嘻</button>
		<script>
			var btn = document.getElementById('btn1');
			btn.onclick = function(){
				alert('哎呀被发现了！')
			}
		</script>
	</body>
</html>